It’s been just over six months since Hurricane Maria slammed into Puerto Rico and roughly 150,000 people still do not have power. A string of grassroots efforts aims to jumpstart the grid with solar energy. Science producer Nsikan Akpan explains what they’ll need to see the light.

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JUDY WOODRUFF:

Finally tonight: It has been just over six months since Hurricane Maria slammed into Puerto Rico, but roughly 150,000 people there still do not have power.

Some are advocating that now is the time for the island to invest in solar energy.

Our science producer, Nsikan Akpan, explains what they will need to see the light in this week's Leading Edge story, which airs every Wednesday.

NSIKAN AKPAN:

When Hurricane Maria hit, Puerto Rico's electric power authority had been relying on imported fossil fuels for 98 percent of its energy. Its major plants beam power from the south to the heavily populated north and west. The storm flooded these power stations, ripped out 65 percent of above-ground cables, and crippled the power supply.

Many are wondering if this commonwealth would be better off being powered by solar. But solar is not an easy fix. Here are four things that Puerto Rico would need to make solar work.

Ingredient one, solar batteries. Solar panels can withstand hurricanes. Even Maria's 155-mile-per-hour winds failed to knock out solar power at the Veterans Medical Center in San Juan. But cloudy weather and the darkness of night keeps solar panels from constantly generating power.

The energy collected during clear days must be stored.

ADAM GENTNER:

So, batteries have made an enormous leap forward in recent years, as with the addition of lithium ion batteries.

NSIKAN AKPAN:

Adam Gentner works for Sonnen, a world leader in solar battery storage.

After Maria, the German company provided free solar batteries and panels at 15 key sites in Puerto Rico. This includes schools, food shelters and this public laundromat in Old San Juan. They picked this site because, after Maria, wastewater wasn't being treated, and washing clothes became lethal.

ADAM GENTNER:

We use lithium iron phosphate, which is — as you can see, it's not a small system for a home, but it's much more resilient to environmental factors. It can discharge and charge up to 10,000 times.

NSIKAN AKPAN:

By packing less energy per square inch, lithium iron phosphate batteries last longer, and are less likely to overheat in Puerto Rico's hot, humid climate.

Gentner expects this $40,000, six-kilowatt-hour battery system at this laundromat to last 26 years. But Puerto Rico's solar emergence will need more than just batteries

Ingredient two, microgrids. Maria crushed 911 emergency communications on the island, so the Las Vegas Fire Department partnered with the nonprofit Empowered by Light and the solar energy company Sunrun to turn these fire stations into solar stations.

MAN:

This is 6,600 watts on this roof. They support an 800-amp-hour, 25-kilowatt-hour battery system. So, it's enough for them to power the radios, the critical parts of this station 24 hours a day, 365 days a year.

NSIKAN AKPAN:

This firehouse in Naguabo is now a microgrid, a self-contained island of power production.

With this microgrid, the city's 30,000 residents can access emergency services even during blackouts. But a microgrid can do more than support a phone line, according to Sunrun's Andy Newbold.

ANDY NEWBOLD:

A lot of times, you're not using all that energy at night, so the excess energy can then feed back into the grid.

NSIKAN AKPAN:

This excess energy can be siphoned into a virtual power plant, a power plant organized in the digital cloud.

ANDY NEWBOLD:

We're working on aggregating all these systems together, so it's hundreds of homes with solar and batteries. And that way, when PREPA or any utility across the country needs it, they can call on us.

NSIKAN AKPAN:

When grouped together, these microgrids can power a whole community or whole cities.

In Germany, one community of 10,000 microgrids produces as much energy as all the coal plants in Texas and West Virginia. But building this type of virtual community requires complex software.

Ingredient number three, a digital oasis.

MANUEL RODRIGUEZ-MARTINEZ:

Oasis is a project that we're running from the university with the goal of designing a new type of smart grid that is decentralized.

NSIKAN AKPAN:

A smart grid is a self-thinking network of microgrids. It can autonomously communicate where energy is being produced, and where to send it.

Manuel Rodriguez-Martinez and a team of computer scientists, electrical engineers and social scientists have spent three years designing a smart grid just for Puerto Rico.

MANUEL RODRIGUEZ-MARTINEZ:

So, rather than just building something and then hoping that people will buy it, the project is trying to understand from a design point of view what people want, and how can I incorporate that feedback into the system.

NSIKAN AKPAN:

They engineered machine-learning algorithms that monitor weather reports to predict how solar panels will perform, and ones that identify power surges before they happen.

Next, they designed a smart card that connects to home power meters, so microgrids can chat something. All this tech then combines with a marketplace app.

MANUEL RODRIGUEZ-MARTINEZ:

Something like eBay, where you can see all the offers available for energy and the time when it is available, and then you can decide from who to buy it.

NSIKAN AKPAN:

But none of this will work without ingredient four, government buy-in.

Puerto Rico's governor announced he wants to privatize and break up the energy utility, with a goal of more than 30 percent renewable energy. But because of the 30-year-old Stafford Act, a law that doles out federal assistance for natural disasters, Puerto Rico's energy system must be rebuilt exactly how it was, same poles, fossil fuel generators and wiring as before.

So it's unclear, at the moment, how solar will integrate into the grid.

ANDY NEWBOLD:

Let's not build poles and wires just to have them knocked down again in the next hurricane. Let's think about smart and resilient energy going forward. We can't keep doing things the same way.

NSIKAN AKPAN:

For the PBS NewsHour, I'm Nsikan Akpan reporting for ScienceScope in Puerto Rico.